The handedness of a particular door installation is determined by the direction in which the door pivots when opened. If a door in the closed position is pivoted counterclockwise to open it, the door installation is considered to be left-handed. On the other hand, a door in a right-handed door installation is pivoted clockwise when opened. When hung from a jamb, a left-handed door would be attached using a left-handed hinge, and a right-handed door a right-handed hinge, unless a non-handed hinge is employed.
In the case of a two-knuckle hinge, in which a pair of hinge leaves each have one hinge knuckle formed on the adjacent edges of two hinge leaves, with one leaf attached to the jamb and the other leaf attached to the door, the hinge leaf associated with the lower hinge-knuckle must be attached to the jamb so that it will support the rest of the hinge assembly. The interface of the lower hinge knuckle and the hinge knuckle on the other hinge leaf, which rests on top of the knuckle attached to the jamb, form a vertical load or thrust bearing to carry the door and provide a surface about which the upper hinge knuckle and leaf may pivot. If one were to attempt to reverse the function of the hinge, however, that is, if a right-handed two-knuckle hinge, for instance, were to be used on a left-handed door installation, the door would have to be hung from the hinge leaf associated with the lower hinge knuckle, and the weight of the door would tend to separate the hinge knuckles rendering the thrust bearing ineffective.
The fact that left or right-handed two-knuckle hinges are not interchangeable is a general marketing drawback, and a non-handed two-knuckle hinge would be preferred. One such hinge has been developed by Charles R. Suska, the inventor herein, and is described in commonly owned U.S. Pat. No. 4,351,085. A two-knuckle non-handed spring hinge is shown and described which has a pair of vertical bearings, one between the adjacent hinge knuckles, and the other located inside the bore of the other hinge knuckle, which pivots about the pintle. A portion of the other bearing is formed on the pintle. Thus, one of the two bearings will always be employed to support the door, depending upon whether the hinge is used in a right-handed or left-handed installation.